1. Field of the Invention
The present invention relates to an object distance display apparatus, and more particularly to an object distance display apparatus for displaying the distance to the object that is focused on by a lens device for television camera use.
2. Description of the Related Art
One of the present inventors has proposed in Japanese Patent Application Nos. 2001-85136 and 2001-285236 (which were, at the time the present invention was made, not published, not publically known, and assigned to the same assignee to which the present invention was subject to an obligation of assignment) object distance display apparatuses in television lens systems used in television cameras for broadcasting use or the like, which display the object distance by acquiring the focusing lens position in which the focusing lens of the lens device is currently set or the focusing lens position designated by a focus controlling device, such as a focus demand, to the lens device and figuring out and displaying the distance to the object that is focused upon in that acquired focusing lens position. Figuring out the object distance requires prior matching between the focusing lens position and the object distance, and the matching can be accomplished, for instance, in the following manner. First, a sample object is arranged in a certain position, the distance from the lens device to that sample object is directly measured, and the focusing lens of the lens device is driven to focus on that sample object. The object distance display apparatus acquires from the lens device the focusing lens position in which it is then set. Now, the actual measurement of the distance to the sample object is entered into the object distance display apparatus. The focusing lens position then set in the lens device is thereby matched with the object distance. By repeating this procedure at different distances of the sample object, a plurality of focusing lens positions and object distances can be matched with each other. According to this matching, a distance function representing the relationship between the focusing lens position and the object distance is figured out, and every position in the whole variable range of the focusing lens position is matched with one object distance or another.
In any of the object distance display apparatuses described above, it is impossible to check the accuracy of the already entered object distance data, and therefore, if a wrong distance is entered by mistake for instance, it is difficult to identify the wrong datum. Especially, unless the object distance displayed according to a wrong datum is evidently abnormal, it is difficult even to notice any error in entered data, and this would invite wrong estimation of the object distance. Even if something wrong in the entered data is noticed, it is impossible to identify the wrong datum, and accordingly there is a problem that the user of the camera would have to take the trouble of deleting all the entered data and enter correct data anew.